Apparatus for deployment of micro-coil using a catheter

ABSTRACT

The apparatus for deployment of a therapeutic device such as a micro-coil detachably mounts the therapeutic device to a distal portion of a pusher member. In one embodiment, the therapeutic device is detachably mounted to the distal portion of the pusher member by a tubular collar that can be heated by a heater such as an electrical resistance coil to expand the collar and release and deploy the therapeutic device. The apparatus for deployment of a therapeutic device such as a micro-coil may also provide for a pusher member and a connector fiber for securing the therapeutic device to the pusher member. The connector fiber passes through a heater within the distal portion of the pusher member, for heating and breaking the connector fiber to release the therapeutic device when a desired placement of the therapeutic device within the vasculature is achieved.

RELATED APPLICATIONS

This is a continuation in part of Ser. No. 09/218,117 filed Dec. 21,1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to devices for interventionaltherapeutic treatment or vascular surgery for treatment of defects inthe vasculature, and more particularly concerns a system and method fordelivering intravascular interventional devices, such as for treatmentof aneurysms.

2. Description of Related Art

Vascular interventional devices such as vasoocclusive devices aretypically placed within the vasculature of the human body by use of acatheter. Vascular interventional devices such as stents can be placedwithin an occluded vessel to facilitate blood flow through the vessel,and vasoocclusive devices are typically either placed within a bloodvessel to block the flow of blood through a vessel making up thatportion of the vasculature through the formation of an embolus, or areplaced within an aneurysm stemming from the vessel to form such anembolus within the aneurysm. Stents can have a wide variety ofconfigurations, but generally need to be placed and then released at adesired location within a blood vessel. Vasoocclusive devices used forthese procedures can also have a wide variety of configurations, andaneurysms have been treated with external surgically placed clips,detachable vasoocclusive balloons and embolus generating vasoocclusivedevices such as one or more vasoocclusive coils.

The delivery of such vasoocclusive devices have typically beenaccomplished by a variety of means, including via a catheter in whichthe device is pushed through an opening at the distal end of thecatheter by a pusher to deploy the device. The vasoocclusive devices canbe produced in such a way that they will pass through the lumen of acatheter in a linear shape and take on a complex shape as originallyformed after being deployed into the area of interest, such as ananeurysm.

One conventional releasable balloon catheter used to embolize vascularlesions has a tube portion made of a material such as a hydrophilicpolymer, located between the catheter and the balloon, that can bemelted by heating the tube, or can be dissolved in the blood whenheated, and electrodes are provided for heating the tube. Anotherconventional technique for separating a balloon from a balloon catheterinvolves the melting and breaking of a connecting member between theballoon and the catheter body, when power is supplied to electrodesprovided for heating the connecting member. When the connecting memberis heated to temperatures of about 70° C. and slight tension is applied,the balloon can be separated from the main catheter body.

An implant delivery assembly is also known that is used for delivery ofimplants such as embolic coils, utilizing a shape memory decouplingmechanism activated when exposed to body temperature. A cooling solutionis flushed through the catheter during introduction and placement of theimplant in order to prevent premature release of the implant prior tothe time that the implant is to be released. Another implant deliveryassembly includes an electrical heating system for heating the couplingmechanism to a temperature at which the shape memory material returns toits original shape, to deploy the implant.

Another device is known in which a device to be implanted is detached byapplication of a high-frequency current which melts and severs a resinthat is used to retain the device to be implanted until the device is tobe deployed. In another known device, an electrolytically severable linkis dissolved by activation of a power source electrically coupled to theelectrolytically severable link to detach the device to be implanted.

In another conventional technique, a conductive guidewire delivers ahigh frequency current through the guidewire to melt and sever a jointto detach an implanted device from the guidewire. The patient isgrounded during the procedure, and current is introduced via theguidewire, rather than with a two way current path.

Such devices that release the interventional device by melting ordissolving the intermediate section between the catheter tip andimplanted device may cause thermal damage of surrounding tissues duringdetachment that can cause embolization in the bloodstream, and may alsopotentially release undesirable particles of materials into thebloodstream that can also cause embolization in the bloodstream. Thereis therefore a need for a precise method of deploying therapeuticinterventional devices without compromising the position of the implant,without causing thermal damage to surrounding tissues, and withoutreleasing undesirable particles of materials into the bloodstream andrisking the formation of emboli in the bloodstream. The presentinvention meets these and other needs.

SUMMARY OF THE INVENTION

Briefly, and in general terms, the present invention provides for anapparatus for deployment of a therapeutic device such as a micro-coilusing a catheter by connecting the therapeutic device to a distalportion of a pusher member. In one presently preferred embodiment, thetherapeutic device is detachably mounted to the distal portion of thepusher member by a tubular collar that can be heated by a heater toexpand the collar and release and deploy the therapeutic device. Inanother presently preferred embodiment, the therapeutic device isdetachably mounted to the distal portion of the pusher member by aconnector thread or fiber passing through a heater provided for heatingand breaking the connector fiber to release the therapeutic device. Inone presently preferred aspect, the heater is advantageously containedsubstantially within the distal portion of the pusher member, whichprovides a sufficient amount of thermal insulation to eliminate thepotential for thermal damages of surrounding tissues during detachment,and since the connecting fiber is heated and broken at a location fullycontained within the distal portion of the pusher member, the potentialfor releasing undesirable particles of materials into the bloodstreamand consequent embolization in the bloodstream is virtually eliminated.

In one presently preferred embodiment, the invention accordinglyprovides for an apparatus for release and deployment of a therapeuticdevice within the vasculature of a patient, comprising an elongated,flexible pusher member having an interior lumen and a distal portion; atubular collar detachably mounting the therapeutic device to the pushermember for placement of the therapeutic device within the vasculature,the tubular collar being expandable when heated and having a closedconfiguration engaging a proximal portion of the therapeutic device andan open configuration releasing the therapeutic device; and a heaterdisposed in the tubular collar of the pusher member for heating thetubular collar to cause the tubular collar to expand and release thetherapeutic device for detaching and deploying the therapeutic devicefrom the flexible pusher member when a desired placement of thetherapeutic device within the vasculature is achieved. In one presentlypreferred aspect, the heater comprises an electrical resistance heatercoil, and may further comprise a power supply and control unit (whichmay be combined in a single unit) to supply electrical current to theheater coil. In a first presently preferred implementation of thetubular collar, the tubular collar is formed from a shape memorymaterial, which may for example be a shape memory polymer, or a shapememory alloy. In another presently preferred implementation of thetubular collar, the tubular collar is formed from a thermoplasticmaterial. The therapeutic device may comprise a vasoocclusive device,such as a microcoil.

The present invention also provides for a method for release anddeployment of a therapeutic device within the vasculature of a patient,wherein a therapeutic device is provided, to be placed within thevasculature of a patient; an elongated, flexible pusher member isprovided, having an interior lumen, and a distal portion; a tubularcollar is provided for detachably mounting the therapeutic device to thepusher member for placement of the therapeutic device within thevasculature, the tubular collar being expandable when heated and havinga closed configuration engaging a proximal portion of the therapeuticdevice and an open configuration when heated releasing the therapeuticdevice; the therapeutic device is positioned at a desired placementwithin a patient's vasculature; and said tubular collar is heated toexpand said tubular collar for detaching and deploying the therapeuticdevice from the flexible pusher member when a desired placement of thetherapeutic device within a patient's vasculature is achieved. In apresently preferred aspect of the method, the step of heating thetubular collar comprises passing electrical current through theelectrical resistance heater to expand the tubular collar.

In another presently preferred embodiment, the invention provides for anapparatus for release and deployment of a therapeutic device within thevasculature of a patient, which comprises an elongated, flexible pushermember having an interior lumen, and a connector fiber detachablymounting the therapeutic device to the pusher member for placement ofthe therapeutic device within the vasculature, the connector fiber beingcapable of being broken by heat. A heater is disposed adjacent to theconnector fiber for heating the connector fiber to cause the connectorfiber to break and release the therapeutic device for detaching anddeploying the therapeutic device from the flexible pusher member when adesired placement of the therapeutic device within the vasculature isachieved. In one currently preferred aspect, the distal portion of thepusher member includes at least one entry port communicating with theinterior lumen, with the heater disposed in the interior lumen of thepusher member adjacent to one or more entry ports. In another presentlypreferred aspect, the connector fiber passes through the heater. In acurrently preferred embodiment, the heater comprises an electricalresistance heater coil, and may also comprise a control unit, with theheater connected by electrical connectors to the control unit forsupplying electrical current to the heater coil. In presently preferredaspects of the apparatus, the flexible pusher member comprises a heatinsulating shaft, and the connector fiber is formed from a thermoplasticmaterial, such as polyethylene.

In one presently preferred embodiment, the therapeutic device to beplaced within the vasculature of a patient is connected to an annularconnector ring, and the connector fiber mounting the therapeutic deviceto the pusher member passes through the connector ring to secure thetherapeutic device to the pusher member. In a currently preferredaspect, the connector fiber extends from a proximal portion of thepusher member to form a loop through the connector ring, and backthrough the one or more ports through the pusher member to the proximalportion of the pusher member. In another presently preferred aspect, thetherapeutic device comprises a vasoocclusive device, such as amicrocoil.

The invention also provides for a method for release and deployment of atherapeutic device within the vasculature of a patient. In the method ofthe invention, a therapeutic device to be placed within the vasculatureof a patient is provided; and an elongated, flexible pusher member. Aconnector fiber detachably mounts the therapeutic device to the pushermember for placement of the therapeutic device within the vasculature,with the connector fiber being capable of being broken by heating, andthe therapeutic device is positioned at a desired placement within apatient's vasculature. Thereafter, a portion of the connector fiber isheated to break the portion of the connector fiber for detaching anddeploying the therapeutic device from the flexible pusher member when adesired placement of the therapeutic device within a patient'svasculature is achieved. In a presently preferred aspect of the method,the portion of the connector fiber to be broken is passed through anelectrical resistance heater disposed within the lumen of the flexiblepusher member, and the step of heating the portion of the connectorfiber comprises passing electrical current through the electricalresistance heater to break the portion of the connector fiber.

These and other aspects and advantages of the invention will becomeapparent from the following detailed description and the accompanyingdrawings, which illustrate by way of example the features of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a first embodiment of the apparatusfor release and deployment of a therapeutic device;

FIG. 2 is a side sectional view of the apparatus of FIG. 1, illustratingrelease of the therapeutic device upon heating of the tubular collar;

FIG. 3 is a top sectional view of a second embodiment of the apparatusfor release and deployment of a therapeutic device;

FIG. 4 is a side sectional view of the apparatus of FIG. 3;

FIG. 5 is a bottom sectional view of the apparatus of FIG. 3;

FIG. 6 is a side sectional view of the apparatus of FIG. 3, illustratingrelease of the therapeutic device upon heating of the elongatedconnector fiber;

FIG. 7 is a side sectional view of a third embodiment of the apparatusfor release and deployment of a therapeutic device;

FIG. 8 is a side sectional view of the apparatus of FIG. 7, illustratingrelease of the therapeutic device upon heating of the elongatedconnector fiber;

FIG. 9 is a side sectional view of a fourth embodiment of the apparatusfor release and deployment of a therapeutic device; and

FIG. 10 is a side sectional view of the apparatus of FIG. 9,illustrating release of the therapeutic device upon heating of theelongated connector fiber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While vasoocclusive devices have conventionally been delivered to aportion of a patient's vasculature to be treated through a deliverycatheter by means of a pusher device, such conventional methods caninvolve separation of the vasoocclusive device from the pusher device inways that result in injury to the vasculature, such as by causingthermal damage of surrounding tissues during detachment that can causeembolization in the bloodstream, or by release of undesirable particlesof materials into the bloodstream that can cause embolization in thebloodstream.

As is illustrated in the drawings, in a first presently preferredembodiment, the invention is embodied in an apparatus for deployment ofa therapeutic device such as a micro-coil using a catheter by connectingthe therapeutic device to a distal portion of a pusher member by atubular collar that can be expanded by heating a portion of the tubularcollar to thereby release the therapeutic device for placement in thevasculature.

With reference to FIGS. 1 and 2, the invention provides for an apparatus10 including an elongated, flexible pusher catheter member 12 forrelease and deployment of a therapeutic device 14 such as avasoocclusive device, and which may for example be a microcoil, only aportion of which is shown. The therapeutic device is typically releasedwithin the vasculature of a patient, introduced through a deliverycatheter 16, for treatment of a target aneurysm. The pusher cathetermember has a shaft defining an interior lumen 18. The therapeutic deviceis typically connected to a stem 20 such as by solder 22, for example,although welding or adhesive, or the like may also be suitable, and thetherapeutic device is mounted and secured to the distal portion of thepusher catheter member by a tubular collar 24 crimped in a closedconfiguration about the proximal end of the stem of the therapeuticdevice, and mounted to the distal end of the pusher catheter, typicallyby adhesive, such as cyanoacrylate adhesive, for example.

In one presently preferred embodiment, the tubular collar is formed froma shape memory polymer (SMP), having a glass transition temperature(T_(g)) above body temperature, such as polyurethane, that can be heattreated to have shape memory behavior.

In another presently preferred embodiment, the collar can be made ofpolymers that are not shape memory polymers, such as polyethyleneterephthalate (PET), polyolefins, fluorocarbons, high densitypolyethylene (HDPE), and other thermoplastic polymers.

In another presently preferred embodiment, the collar can be made of ashape memory alloy spring at the distal end of the catheter. The shapememory alloy can for example be a shape memory metal such as nickeltitanium alloy, such as that available under the trade name NITINOL, forexample, that can be heat treated to have shape memory behavior. Whenthe current is applied through the connector, the shape memory alloyspring will transform from a martensitic state to an austenitic state,to release the coil socket from the shape memory alloy spring.

A heater, such as an electrical resistance heater coil 26, is disposedwithin the collar, and is connected by electrical connectors 28extending through the lumen of the pusher catheter to a power supply 30which can in turn be operated by a control unit 32. The power supply andcontrol unit may optionally be combined. The resistance heater coil canbe fabricated from platinum, stainless steel, or other high resistancematerials, and the electrical connectors, can be copper or other highlyelectrically conductive leads that extend to the proximal part of thepusher catheter assembly. The power supply may be quite small, housing asmall battery, for example, that is sufficient to supply electricalcurrent to the heater coil to cause the collar to expand due to theapplication of heat, and release the therapeutic device, as isillustrated in FIG. 2. Alternatively, the heater may deliver heat to thetubular collar by other means, such as thermo-mechanical,electromagnetic or RF energy, for example. The lumen and collar of thepusher catheter member advantageously provides an insulative space andwall thickness to contain the heating of the collar to avoid thermaldamage to surrounding tissues during heating of the collar to deploy thetherapeutic device. Additionally, most of the pusher catheter member issurrounded by a guiding or delivery catheter, so that the heating of thecollar does not come in contact with tissue.

In another presently preferred embodiment, the invention is embodied inan apparatus for deployment of a therapeutic device such as a micro-coilusing a catheter by connecting the therapeutic device to a distalportion of a pusher member by a connector fiber that can be broken byheating a portion of the connector fiber to break the connector fiberand thereby release the therapeutic device for placement in thevasculature.

With reference to FIGS. 3-6, in another presently preferred embodiment,the invention provides for an apparatus 40 including an elongated,flexible pusher member 42 for release and deployment of a therapeuticdevice 44 such as a vasoocclusive device, which may for example be amicrocoil, only a portion of which is shown, within the vasculature of apatient, through a delivery catheter 46. The pusher member has a shaft47 that provides a measure of thermal insulation to an interior lumen48, as will be further explained below. The shaft of the pusher membertypically has an outer diameter of approximately 0.015″, and an insidediameter of approximately 0.007, and can be formed from polyethyleneterephthalate (PET) tubing. The pusher member has a distal portion 50with entry ports 52 in communication with the interior lumen, and a plug54 at the distal end of the pusher member, typically secured within thedistal end of the pusher member by adhesive, such as a cyanoacrylateadhesive, for example.

The therapeutic device is typically connected to a stem 56 such as bysolder 58, and the stem is in turn connected to an annular connectorring 60, typically by an adhesive such as a cyanoacrylate adhesive, forexample. The therapeutic device is mounted and secured to the distalportion of the pusher member by an elongated connector thread or fiber62 extending from a proximal portion of the pusher member to form a loop64 through the connector ring, and extending back through the entryports of the pusher member to the proximal portion of the pusher member.In a presently preferred embodiment, the connector fiber is formed ofpolyethylene, and is typically about 0.015 to 0.030 inches in diameter,although the connector fiber can be as thin as about 0.0005 inches indiameter, and can be formed from a variety of thermoplastic materialswith high tensile strength and suitable melt temperatures. The connectorfiber may also optionally be formed of a suitable high tensile strengthmaterial, such as a biodegradable material, for example, that wouldmerely degrade or decompose to break upon being heated.

A portion of the connector fiber to be broken to deploy the therapeuticdevice passes through a heater, such as a resistive heater coil 66connected by electrical connectors 68 to a control unit 70 whichsupplies electrical current to the heater coil to cause the connectorfiber to break and release the therapeutic device. Alternatively, theheater may deliver heat to the connector fiber by other means, such asthermo-mechanical, electromagnetic or RF energy, for example. The lumenof the pusher member advantageously provides an insulative space andwall thickness to contain the heating of the connector fiber to avoidthermal damage to surrounding tissues, and to help contain pieces of theconnector fiber that may be formed during heating of the connector fiberto deploy the therapeutic device.

With reference to FIGS. 7 and 8, in another presently preferredembodiment, the invention provides for an apparatus 80 including anelongated, flexible pusher catheter member 82 for release and deploymentof a therapeutic device 84 such as a vasoocclusive device, which may forexample be a microcoil, only a portion of which is shown, within thevasculature of a patient, through a guiding or delivery catheter 86. Thepusher catheter member has a shaft 87 that is currently preferablyformed from a PET lamination, and an inner elongated coaxial mandrel 90typically formed of stainless steel, which may extend distally beyondthe shaft of the pusher catheter member.

The therapeutic device is typically connected to a stem 96 such as bysolder 98, and the stem is in turn connected to an annular connectorring 100, typically by an adhesive such as a cyanoacrylate adhesive, forexample. The therapeutic device is mounted and secured to the distalportion of the pusher member by an elongated connector thread or fiber102 extending distally from the pusher catheter member shaft over thedistal portion of the mandrel to form a loop 104 through the connectorring, and extending back toward the pusher catheter member shaft. Theelongated connector fiber is retained over the mandrel by one or moreannular rings or collars 105, typically formed of PET. In a presentlypreferred embodiment, the connector fiber is formed of polyethylene,such as a medium density polyethylene, and is typically about 0.015 to0.030 inches in diameter, although the connector fiber can be as thin asabout 0.0005 inches in diameter, and can be formed from a variety ofthermoplastic materials with high tensile strength and suitable melttemperatures. The connector fiber may also optionally be formed of asuitable high tensile strength material, such as a biodegradablematerial, for example, that would merely degrade or decompose to breakupon being heated.

A portion of the connector fiber to be broken to deploy the therapeuticdevice passes through a heater, such as a resistive heater coil 106connected by electrical connectors 108, typically formed by copper wirewith a polyamide casing, extending to a control unit 110 which supplieselectrical current to the heater coil to cause the connector fiber tobreak and release the therapeutic device. The heater coil preferablyfits closely around the connector fiber. Alternatively, the heater maydeliver heat to the connector fiber by other means, such asthermo-mechanical, electromagnetic or RF energy, for example. The lumenof the pusher member advantageously provides an insulative space andwall thickness to contain the heating of the connector fiber to avoidthermal damage to surrounding tissues, and to help contain pieces of theconnector fiber that may be formed during heating of the connector fiberto deploy the therapeutic device.

With reference to FIGS. 9 and 10, in another presently preferredembodiment, the invention provides for an apparatus 120 including anelongated, flexible pusher catheter member 122 for release anddeployment of a therapeutic device 124 such as a vasoocclusive device,which may for example be a microcoil, only a portion of which is shown,within the vasculature of a patient, through a guiding or deliverycatheter 126. The pusher catheter member has a shaft 127 that is open atits distal end.

The therapeutic device is typically connected to a stem 136 such as bysolder 138, and the stem is in turn connected to an annular connectorring 140, typically by an adhesive such as a cyanoacrylate adhesive, forexample. The therapeutic device is mounted and secured to the distalportion of the pusher member by an elongated connector thread or fiber142 extending distally over pusher catheter member shaft to form a loop144 through the connector ring, and extending back proximally over thepusher catheter member shaft. In a presently preferred embodiment, theconnector fiber is formed of polyethylene, such as a medium densitypolyethylene, and is typically about 0.015 to 0.030 inches in diameter,although the connector fiber can be as thin as about 0.0005 inches indiameter, and can be formed from a variety of thermoplastic materialswith high tensile strength and suitable melt temperatures. The connectorfiber may also optionally be formed of a suitable high tensile strengthmaterial, such as a biodegradable material, for example, that wouldmerely degrade or decompose to break upon being heated.

A portion of the connector fiber to be broken to deploy the therapeuticdevice passes through a heater, such as a resistive heater coil 146connected by electrical connectors 148 extending to a control unit 150which supplies electrical current to the heater coil to cause theconnector fiber to break and release the therapeutic device. The heatercoil preferably fits closely around the connector fiber. Alternatively,the heater may deliver heat to the connector fiber by other means, suchas thermo-mechanical, electromagnetic or RF energy, for example. Thelumen of the pusher member advantageously provides an insulative spaceand wall thickness to contain the heating of the connector fiber toavoid thermal damage to surrounding tissues, and to help contain piecesof the connector fiber that may be formed during heating of theconnector fiber to deploy the therapeutic device.

It will be apparent from the foregoing that while particular forms ofthe invention have been illustrated and described, various modificationscan be made without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the invention belimited, except as by the appended claims.

1-48. (canceled)
 49. An apparatus for release and deployment of atherapeutic device within the vasculature of a patient, comprising: anelongated, flexible pusher member having an interior lumen and a distalportion; a tubular collar detachably mounting the therapeutic device tothe pusher member for placement of the therapeutic device within thevasculature, the tubular collar being expandable when heated and havinga closed configuration engaging a proximal portion of the therapeuticdevice and an open configuration releasing the therapeutic device; aheater disposed in the tubular collar of the pusher member for heatingthe tubular collar to cause the tubular collar to expand and release thetherapeutic device for detaching and deploying the therapeutic devicefrom the flexible pusher member when a desired placement of thetherapeutic device within the vasculature is achieved, said interiorlumen of said elongated, flexible pusher member and said tubular collarbeing configured to provide an insulative space and wall thickness tocontain heating of said tubular collar to avoid thermal damage tosurrounding tissues of the vasculature of the patient.
 50. The apparatusof claim 49, wherein said heater comprises an electrical resistanceheater coil.
 51. The apparatus of claim 49, further comprising a controlunit, and wherein said heater is connected by electrical connectors tothe control unit which supplies electrical current to the heater coil.52. The apparatus of claim 49, wherein said tubular collar is formedfrom a shape memory material.
 53. The apparatus of claim 52, whereinsaid shape memory material is a shape memory polymer.
 54. The apparatusof claim 52, wherein said shape memory material is a shape memory alloy.55. The apparatus of claim 49, wherein said tubular collar is formedfrom a thermoplastic material.
 56. The apparatus of claim 49, whereinsaid therapeutic device comprises a vasoocclusive device.
 57. Theapparatus of claim 49, wherein said therapeutic device comprises amicrocoil.
 58. An apparatus for release and deployment of avasoocclusive device within the vasculature of a patient, comprising: anelongated, flexible pusher member having an interior lumen and a distalportion; a tubular collar detachably mounting the vasoocclusive deviceto the pusher member for placement of the vasoocclusive device withinthe vasculature, the tubular collar being expandable when heated andhaving a closed configuration engaging a proximal portion of thevasoocclusive device and an open configuration releasing thevasoocclusive device; a heater disposed in the tubular collar of thepusher member for heating the tubular collar to cause the tubular collarto expand and release the vasoocclusive device for detaching anddeploying the vasoocclusive device from the flexible pusher member whena desired placement of the vasoocclusive device within the vasculatureis achieved, said interior lumen of said elongated, flexible pushermember and said tubular collar being configured to provide an insulativespace and wall thickness to contain heating of said tubular collar toavoid thermal damage to surrounding tissues of the vasculature of thepatient.
 59. The apparatus of claim 58, wherein said heater comprises anelectrical resistance heater coil.
 60. The apparatus of claim 58,further comprising a control unit, and wherein said heater is connectedby electrical connectors to the control unit which supplies electricalcurrent to the heater coil.
 61. The apparatus of claim 58, wherein saidtubular collar is formed from a shape memory material.
 62. The apparatusof claim 61, wherein said shape memory material is a shape memorypolymer.
 63. The apparatus of claim 61, wherein said shape memorymaterial is a shape memory alloy.
 64. The apparatus of claim 58, whereinsaid tubular collar is formed from a thermoplastic material.
 65. Theapparatus of claim 58, wherein said vasoocclusive device comprises amicrocoil.
 66. A method for release and deployment of a therapeuticdevice within the vasculature of a patient, the steps of the methodcomprising: providing a therapeutic device to be placed within thevasculature of a patient; providing an elongated, flexible pushermember, having an interior lumen, and a distal portion; providing atubular collar detachably mounting the therapeutic device to the pushermember for placement of the therapeutic device within the vasculature,the tubular collar being expandable when heated and having a closedconfiguration engaging a proximal portion of the therapeutic device andan open configuration when heated releasing the therapeutic device;positioning the therapeutic device at a desired placement within apatient's vasculature; and heating a portion of said tubular collarwithin said interior lumen of said flexible pusher member to expand saidtubular collar for detaching and deploying the therapeutic device fromthe flexible pusher member when a desired placement of the therapeuticdevice within a patient's vasculature is achieved, said interior lumenof said elongated, flexible pusher member and said tubular collarproviding an insulative space and wall thickness to contain heating ofsaid tubular collar to avoid thermal damage to surrounding tissues ofthe vasculature of the patient.
 67. The method of claim 66, wherein saidstep of heating said tubular collar comprises passing electrical currentthrough said electrical resistance heater to expand said tubular collar.68. The method of claim 66, wherein said therapeutic device comprises avasoocclusive device.
 69. The method of claim 66, wherein saidtherapeutic device comprises a microcoil.